The present invention relates to a structure for securing an electric motor to a chassis and a disc drive apparatus using the structure. More particularly, the invention relates to a structure that makes it easy to adjust the angle at which a motor is secured to a chassis and reliably holds the motor at the angle adjusted, and also a disc drive apparatus that comprises the structure.
Disc drive apparatuses writes and reads data on and from recording media shaped like a disc. More precisely, the optical pickup emitting and receiving a laser beam incorporated in the disc drive apparatus writes data on a disc-shaped recording medium and reads data therefrom. To write and read data on and from the disc-shaped recording medium correctly, the optical pickup needs to have its optical axis crossing the signal-recording surface of the disc-shaped recording medium, exactly at right angles.
To adjust the angle between the optical axis of the optical pickup and the signal-recording surface of the disc-shaped recording medium, two types of adjustment should be performed. First, the angle at which optical axis inclines to the diameter (radial direction) of the disc-shaped recording medium must be adjusted. Second, the angle at which optical axis inclines to the tangential direction of the recording tracks provided on the disc-shaped recording medium must be adjusted.
Two methods of adjusting the angle of the optical axis of the pickup are available. The first method is to adjust the position of the optical pickup. The second method is to adjust the position of the disc-shaped recording medium.
The first method will be described. The optical pickup is movably supported on two guide shafts. The guide shafts are supported on the chassis such that the distance between the ends of the guide shafts can be freely changed. The distances are changed to adjust the optical pickup takes with respect to the chassis. Let us assume that the distance between the chassis and those ends of the guide shafts, which lie on the same side, at an inner recording track of the disc-shaped recording medium, is changed. In this case, the position of the optical axis is adjusted in the radial direction of the recording tracks. On the other hand, if the distance between the ends of only one guide shaft is changed, the position of the optical axis is adjusted in the tangential direction of the recording tracks. In either case, we can adjust the skew that the optical axis of the pickup has with respect to the signal-recording surface of the disc-shaped recording medium.
The second method is used in the case where a spindle motor is secured to a motor substrate fastened to the chassis with adjustment screws (usually, three screws) and a turntable is mounted on the shaft of the spindle motor to hold the disc-shaped recording medium. Coil springs are mounted on the adjustment screws and interposed between the chassis and the motor substrate. Turning the adjustment screws can change the position the spindle motor assumes to the chassis. Namely, turning the adjustment screws can adjust the angle at which the spindle motor is secured to the chassis. The position of the optical axis can thereby adjusted in the radial and tangential directions of the recording tracks. This adjusts the skew that the optical axis of the pickup has with respect to the signal-recording surface of the disc-shaped recording medium.
In the first method, the guide shafts are moved to adjust the position of the optical axis in the tangential and radial directions of the recording tracks. Hence, the optical axis will incline to both the radial direction and the tangential direction when one adjustment screw is turned. Once one adjustment screw is turned, the other adjustment screws must be turned. Obviously it would be difficult to adjust the skew of the optical axis.
Further, the skew adjustment must be carried out in different ways when the optical pickup is at an inner recording track of the disc-shaped recording medium and when it is at an outer recording track of the recording medium. This renders the skew adjustment intricate and cumbersome.
Since the guide shafts extend a long distance along the diameter of the disc-shaped recording medium, the adjustment screws must be turned many times to incline the guide shafts at a prescribed desired angle, thereby to adjust the position of the optical head in the tangential and radial direction of the recording tracks. The distance (displacement) the adjustment screws must be moved in the vertical direction is inevitably long as compared to the change of skew angle. This makes it difficult to decrease the thickness of the disc drive apparatus.
In the second method, elastic members such as coil springs are indispensable to the structure of securing the motor substrate to the chassis, for the purpose of adjusting the angle at which the spindle motor is secured to the chassis. Moreover, the spindle motor is a source of vibration. Due to the use of elastic members and the vibration generated by the spindle motor, the motor substrate cannot be stable in position with respect to the chassis.
An object of this invention is to provide a motor-securing structure that can adjust the angle at which an electric motor is secured to a chassis and can secure the motor to the chassis steadfast such that the motor generates no vibration even if its position is adjusted.
Another object of the invention is to provide a disc drive apparatus in which the skew angle the optical pickup has with respect to the disc-shaped recording medium can be easily and quickly adjusted in both the tangential direction and radial direction of the recording tracks provided on the recording medium, and in which the distance or displacement the adjustment screws must be moved is short enough to decrease the thickness of the apparatus.
To achieve these objects, a motor-securing structure according to the invention is designed to secure an electric motor supported on a motor substrate to a chassis. The structure comprises: at least three coupling sections which couple the motor substrate and the chassis to each other, at least two of said coupling sections being fixed support members which hold and space the motor substrate and the chassis from each other at a prescribed distance, and the remaining coupling section being an adjusting support member which holds the motor substrate and the chassis from each other at a variable distance; and rigid holding means incorporated in the adjusting support member, for holding the motor substrate and the chassis so that the motor substrate and the chassis remain rigid.
When the adjusting support member is operated, adjusting the distance between the motor substrate and the chassis, the angle at which the motor is inclined to the chassis is changed. Once the angle is thus changed, the motor substrate and the chassis are held and remain rigid. This suppresses a vibration problem that may generally results from the spindle motor that is a source of vibration.
A disc drive apparatus according to this invention comprises: a turntable for holding a disc-shaped recording medium; a spindle motor for rotating the turntable; an optical pickup for reading and writing data on and from the disc-shaped recording medium; guide shafts supporting the optical pickup, allowing the optical pickup to move in a radial direction of the disc-shaped recording medium; a thread motor for moving the optical pickup; a tangential-skew adjusting mechanism for adjusting a skew of an optical axis of the optical pickup, mainly with respect to a tangential direction (of the recording tracks of the disc-shaped recording medium); and a radial-skew adjusting mechanism for adjusting a skew of the optical axis of the optical pickup, mainly with respect to a radial direction (of the recording tracks of the disc-shaped recording medium).
In the disc drive apparatus of the invention, the skew of the optical axis of the pickup with respect to the disc-shaped recording medium can be adjusted in the tangential direction of the recording tracks, and almost independently in the radial direction thereof. Hence, the inclination of the optical axis can be adjusted easily and quickly.
The other objects and other advantages of the invention will be more apparent from the following description of the embodiments.